The present invention relates to maintenance of remote structures, and more particularly to the controlled application of a fluidic media in connection with such maintenance.
The manipulation of loads in connection with tower structure construction and maintenance is a key to the viability of such structures. For example, some important structures have been erected at remote and foreboding sites only because it has been possible to fly the components to each site by helicopter, the parts being attached to each structure while the helicopter hovers with the load properly positioned and oriented. See, for example, U.S. Pat. No. 4,378,919 to H. Smith that discloses apparatus by which a load suspended from a helicopter is free to swing beneath the helicopter, yet the rotational position of the load about a vertical axis is controlled by yaw manipulation of PG,3 the helicopter. The Smith disclosure includes a yoke by which the load is suspended on a pair of cables, the yoke being restrained from rotation under the helicopter by a ring-shaped tubular structure that forms a pair of slots for receiving opposite ends of the yoke. A linkage allows the tubular structure to move back and forth in response to swinging of the cargo hook.
The Smith device is subject to several disadvantages. For example, the linkage is somewhat complex, having several swinging joints. Also, the slot in the tubular structure must provide extra clearance for the yoke to allow for lateral tipping of the tubular structure, reducing the effectiveness of the structure in yaw control. Further, anchor points for the linkage must be provided on the aircraft structure. Moreover, there are times when further control of a suspended load beyond mere rotational control is needed. For example, in one aspect of tower structure maintenance, it is desired to clean critical portions of the structure, such as insulators of power high voltage power transmission towers.
Presently, the insulators are cleaned at relatively long range using deionized water at high pressure. This can be done from the ground using what amounts to a fire truck, and a man carrying a hose can also climb the tower. Attempts to do this from the air have had limited success because water is too heavy for economical transport by helicopter, and a second crew member is required for operating a nozzle turret that is needed for directing the stream sufficiently accurately. This greatly increases the of weight to the load, and the hardware is expensive. The expense of the hardware is aggravated by the need for of FAA certification. See, for example, U.S. Pat. No. 4,477,239 to Kurtgis that discloses a tower insulator cleaning apparatus that is carried by helicopter. Also, when the helicopter is large enough for carrying a meaningful load, two pilots are required under FAA regulations.
Water creates its own problems in that when it is contaminated by dirt from the insulator, it becomes conductive, creating a danger of arcing. Moreover, there are large reactive forces to contend with. "Dry cleaning" has also been done using a blast of air and particles of walnut shells, sand, corn husks or the like. But the air blast has a short range of only two or three feet, tending to preclude effective cleaning from a nozzle mounted on the helicopter, which must fly close to the wires. Also, when hoses are used, such as by a man climbing the tower, the losses are prohibitive.
As mentioned above, a disadvantage of the Kurtgis apparatus is that at least two crew members are required, and only a relatively small quantity of the liquid spray can be carried. Also, the helicopter must fly at a low altitude approximately corresponding to the height of each insulator to be cleaned. This presents the danger that a gust of wind or other emergency might cause the helicopter to crash into the tower and/or the transmission lines, with disastrous consequences. Moreover, the center insulator on a conventional "single circuit" tower is nearly inaccessible from the side, and must be cleaned at long range.
A further disadvantage of the Kurtgis apparatus is that the nozzle is located at the end of a long boom for clearing the ends of the rotor blades. This makes the nozzle particularly difficult to aim accurately. This difficulty is aggravated by the independent control of the position and orientation of the helicopter by its pilot, and the separate aiming of the nozzle in both yaw and elevation by the boom operator. Moreover, the nozzle and/or the boom can get caught in the tower, with the consequent likelihood of crashing the helicopter because neither the boom with its nozzle, nor the remainder of the heavy cleaning apparatus and its operator can be released in an emergency.
Another use for the controlled dispensing of a media onto a remote workpiece is in fighting fires. See, for example, U.S. Pat. No. 2,779,421 to Rust, disclosing an aerial fire extinguisher, and U.S. Pat. No. 4,090,567 to Tomlinson, disclosing a fire fighting helicopter.
A disadvantage of these firefighting systems is that the full weight of the applied medium must be carried by the helicopter. A further disadvantage of the Rust fire extinguisher is that there is little control of either the location or the amount of the applied media, because the media is applied by a plurality of outwardly directed nozzles that rotate about a central vertical axis, and because the full load is dispensed upon release of a valve by ground contact.
A further disadvantage of the Tomlinson system is that at least two crew members are required as with the cleaning system of Kurtgis, discussed above. Directional control of the stream of media is difficult to maintain, as with the Kurtgis apparatus, because the orientation of a boom nozzle dispensing the media depends on the actions of both the pilot and the boom operator. Moreover, apparatus controlling the relative position of the nozzle is bulky, excessively heavy, slow to respond, and expensive to provide because the relatively long boom for the nozzle must be moved about in its entirety for aiming the nozzle.
Thus there is a need for a highly mobile apparatus for dispensing a fluidic medium, accurately in both yaw and elevation. Also, there is a need for such apparatus to be capable of delivering controlled amounts of a large effective quantity of the media. There is a further need that such apparatus be safe to operate in close proximity to high voltage power transmission lines and towers, and be adapted for effectively and rapidly cleaning large numbers of tower components, as well as being inexpensive to build and easy to operate.